As a system to encode a stereo audio signal at a low bit rate, an intensity stereo system is known. In the intensity stereo system, an L channel signal (left channel signal) and an R channel signal (right channel signal) are generated by multiplying a monaural signal by a scaling factor. This type of technology is referred also as an amplitude panning.
The most basic technology of the amplitude panning multiplies a monaural signal in a time domain by a gain factor for the amplitude panning (panning gain factor) to calculate the L channel signal and the R channel signal (e.g. see non patent literature 1). Further, as another technology, the monaural signal may be multiplied by the panning gain factor to calculate the L channel signal and the R channel signal for each of frequency components (or each of frequency groups) in a frequency domain (e.g. see non patent literature 2).
When the panning gain factor is used as an encoding parameter of a parametric stereo, a scalable encoding of a stereo signal (monaural-stereo scalable encoding) can be realized (e.g. see patent literature 1 and patent literature 2). The panning gain factor is explained as a balance parameter in patent literature 1, and is explained as an ILD (level difference) in patent literature 2, respectively.
Note that the balance parameters are defined as a gain factor to multiply with the monaural signal upon converting the monaural signal to the stereo signal, and this corresponds to the panning gain factor (gain factor) in amplitude panning.